Secondary batteries are rechargeable unlike primarily batteries, and also, the possibility of compact size and high capacity is high. Thus, recently, many studies on secondary batteries are being carried out. As technology development and demands for mobile devices increase, demands for rechargeable batteries as energy source are rapidly increasing.
In such a secondary battery, an electrode assembly may be built in a battery case. The electrode assembly mounted in the battery case is a chargeable and dischargeable power generating device having a structure in which a positive electrode/a separator/a negative electrode are stacked.
In recent years, free form batteries having various shapes are being widely used due to the appearance of various electronic devices. To freely realize shapes of batteries, it may also be necessary to manufacture the electrode assembly provided in the battery into various shapes.
FIG. 1 is a perspective view of an electrode assembly in a state in which electrode tabs are boded to each other to form a tab bonding part in the electrode assembly according to the related art. FIG. 2 is a perspective view illustrating a state in which an electrode lead is connected to the tap bonding part in FIG. 1. FIG. 3 is a plan view of FIG. 2 when viewed from an upper side.
Referring to FIG. 1, an electrode assembly 1 comprising a first electrode unit 10 and a second electrode unit 30 having a size less than that of the first electrode unit 10 and staked on the first electrode unit 10 is illustrated in FIG. 1.
In the electrode assembly 1, positive electrode tabs of the first electrode unit 10 and positive electrode tabs of the second electrode unit 30 are connected to each other to form a positive electrode tab bonding part 51. Also, negative electrode tabs of the first electrode unit 10 and negative electrode tabs of the second electrode unit 30 may also be connected to the other to from a negative electrode tab bonding part 53.
When the positive electrode tab bonding part 51 and the negative electrode tab bonding part 53 are formed, the first electrode unit 10 and the second electrode unit 30 may be electrically connected to each other. Thus, the electrode assembly 1 having large capacity corresponding to the sum of those of the first and second electrode units 10 and 30 may be manufactured.
Referring to FIG. 2, a positive electrode lead 81 and a negative electrode lead 83 may be connected to the electrode assembly 1 to electrically connect the outside of the battery to the electrode assembly 1 within the battery. The positive electrode lead 81 may be connected to the positive electrode tab bonding part 51, and the negative electrode lead 83 may be connected to the negative electrode tab bonding part 53.
Here, positions of the electrode tabs to which the electrode leads 81 and 83 are connected have to be defined within a range J illustrated in FIG. 3.
This is done because, when the electrode tab of the first electrode unit 10 is directly connected to the electrode tab of the second electrode unit 30, the electrode tab of the first electrode unit 10 has to be disposed within the range J of a width of the second electrode unit 30. Thus, all the electrode tab of the first electrode unit 10 and the electrode tab of the second electrode unit 30 have to be disposed within the range J.
As described above, since the range of the position of the electrode tab, at which the electrode lead is capable of being connected to a free form battery, is narrowly limited in the related art, a degree of freedom in design of a secondary battery or a battery pack may be significantly reduced.